Field of Invention
The present invention relates to a spray coater and a ring-shaped structure of the spray coater.
Description of Related Art
A typical spray coater includes a vacuum chuck, plural ring-shaped bodies and a nozzle. The ring-shaped bodies surround the vacuum chuck. When a wafer is located on the vacuum chuck, the nozzle can spray photoresist on a front surface of the wafer. In addition, redundant photoresist may flow to the ring-shaped bodies from the wafer. Thereafter, the redundant photoresist flows out of the spray coater from the ring-shaped bodies.
When the photoresist flows to an edge of the wafer from the front surface of the wafer, airflow generated by the vacuum chuck enables the photoresist to flow to a back surface of the wafer from the edge of the wafer, which is referred to as a “vacuum effect”. Since the diameter of the wafer is about 10 mm greater than the outer diameter of the innermost ring-shaped body and the innermost ring-shaped body does not have a special design, the photoresist is left on the edge of the back surface of the wafer with a width of about 15 mm. As a result, the photoresist enters a trench of the wafer. In a subsequent manufacturing process, a knife is used to cut the wafer along the trench.
In a subsequent etching process, the photoresist left on the edge of the back surface of the wafer results in photoresist burning (PR burn), thus reducing the yield rate of the wafer. Moreover, the photoresist is also left on the vacuum chuck to cause abnormal vacuuming. In addition, the innermost ring-shaped body is made of aluminum, so that the strength of the innermost ring-shaped body is not enough and is easily deformed. As a result, the reliability of the spray coater is reduced.